Mar 08, 2021
The status quo, development and selection of UPS power supply
After more than a century of development, electricity has become the most important energy foundation for modern industry. With the continuous progress of industrial civilization, modern industry has increasingly higher requirements for power quality. In order to ensure the continuity of industrial processes and daily work, UPS came into being and successfully solved the problems of power interruption and poor power quality. It is widely used in industrial control, communication, medical treatment, computer, transportation, banking, securities, etc.
Current status of 1UPS
After decades of development, UPS technology has changed rapidly, the management system has been continuously improved, the functions have become more powerful, and the scope of application has also been continuously expanded with the development of modern technology.
1.1 Technical aspects
(1) Generalized soft switching technology, which is different from traditional resonant ZUS and ZCS soft switching, has been widely used to reduce switching loss and increase switching frequency. This kind of soft switch is a lossless snubber circuit, which can not only soften the switching process, but also has the characteristics of simple circuit, no additional resonance network, and low cost. The input end is equipped with high-efficiency input filter and active power factor corrector, and adopts series-parallel compensation technology to reduce the input current distortion, reduce the pollution of the UPS power supply to the mains power supply, and make it develop into a green power conversion type.
(2) In order to realize the miniaturization of UPS power supply, reduce the size of the output transformer, that is, the output filter, reduce electromagnetic interference, and prevent the saturation of high-frequency transformers, the series resonant inverter is currently used in South Korea, and the isolation transformer and The frequency converter forms a high-frequency connected UPS.
(3) Digital control has become the mainstream of the development of new UPS control technology, that is, the digital processor DSP is widely used, and the control circuit is fully microprocessor-based as much as possible. Because the digital controller has high precision and strong anti-interference ability, it is easy to realize the detection, fault diagnosis and isolation of the UPS, easy to realize remote control and telemetry, easy to realize the parallel connection and hot swap of multiple UPSs, and easy to realize the monitoring and management of the battery That is to say, the intervention of the computer can make the UPS realize intelligent management, which can make the power supply run in the optimal state.
(4) The battery is the heart of UPS. At present, UPS generally uses maintenance-free sealed lead-acid batteries. The United States also uses high-power lead-air backup power units (RPU) to replace batteries. In order to increase the service life of the battery, a three-stage battery management scheme is currently used, namely constant current balanced charging, floating charge charging and natural discharge to prevent overcharge and overdischarge. A battery management system based on microprocessor monitoring technology has been introduced to observe the charging and discharging status of the battery at any time, and to double-protect the battery charging and discharging.
(5) Redundancy technology and hot plug technology are used.
(6) Adopt intelligent UPS management system. The so-called intelligent UPS refers to the hardware interface that connects the traditional UPS to the computer, combined with specially designed software, to provide double protection of the computer and data, ensuring that the UPS can detect all faults in addition to completing the basic functions. Display and processing, etc., fully realize networked monitoring and management.
1.2 Management system
The UPS power supply system has been in existence for more than 40 years, 40 years of history, the development of UPS is no longer the development of isolated power supply technology, UPS itself is no longer a separate power supply system, the current so-called power supply room has become An integrated network system, a complete set of power supply and management solutions that integrate uninterrupted power supply, cabinets, power management, heat dissipation, power cables and data wiring. This greatly facilitates the user's purchase, installation, maintenance and expansion, reduces the cost of daily management and maintenance, and can comprehensively protect the hardware equipment, operating programs and data in the entire network, and the data transmission path, making it a Uninterrupted power supply network, this network also has high reliability, strong anti-interference ability, strong overload ability, intelligent monitoring, lightning protection, surge protection and other functions.
1.3 Design principles and working methods
There are currently three types of UPS: offline, online, and online interactive.
(1) Offline UPS, also known as backup UPS, is mainly low-power (5kVA). The main features are high conversion efficiency, easy maintenance, and low price. The conversion time is a few ms, which is the majority of small and medium power users. Preferred.
(2) On-line UPS is mainly based on large and medium power (above 5kVA), the power supply conversion time is zero, and the power supply quality is high. It can provide the user's load with pure, stable, frequency stable, anti-interference and minimal waveform distortion. Wave, but expensive.
(3) The online interactive UPS is mainly used in the network. It combines the characteristics of high conversion efficiency of the offline type and high quality of the online power supply. Compared with the offline type, the switching time is short.
1.4 Functional aspects
In addition to the basic functions of voltage stabilization, frequency stabilization, and uninterrupted power supply, UPS has gradually added self-control function, external alarm function, centralized monitoring function, environmental detection function, automatic switch machine function, networking function, battery automatic compensation and detection function, Low power loss function, direct parallel function, the function of having the same output for linear load and non-linear load, and the function of using battery or separate battery when paralleling.
1.5 Application aspects
On the basis of the original commercial UPS, inverter UPS, and industrial UPS, in order to meet the needs of the market, UPS for computers, UPS for cable TV, and UPS for PHS have been added. Therefore, UPS has been widely used in finance, telecommunications, government, manufacturing, education, and medical care.
Market demand has promoted the continuous improvement of UPS performance, and technological progress has promoted the continuous forward development of UPS technology, making UPS to high-frequency, redundant parallel, digital, reliable, intelligent, green, and economical. development of. 2.1 In terms of market demand
(1) Large-capacity UPS will reach the demand of 9,000 units per year, and it will continue to grow at a rate of more than 10%. The small machine market is "hot" and the market potential is huge. According to estimates by relevant persons, the demand for UPS power supply is: 938 thousand units/in 2005, 1.025 million units/in 2006, 1.34 million units/in 2007, and 1.223 million units/in 2008.
(2) Product performance/price ratio is the eternal theme of winning market share.
(3) If an enterprise wants to go out of transnational operation, it must not only create an international brand, but also "localize" the brand in the transnational operation. In order to achieve long-term development in the market, in addition to improving cost performance, it is also necessary to improve service quality in order to adapt to the merger and integration state of deep-level product competition in the market.
2.1 Technical aspects
(1) High frequency: The power switch of the first generation UPS is a thyristor, the second generation is a high-power transistor or field effect tube, and the third generation is an IGBT (insulated gate bipolar transistor). The switching speed of high-power transistors or field-effect transistors is an order of magnitude higher than that of thyristors, and the current capacity and speed of IGBT power devices are much larger and faster than those of high-power transistors or field-effect transistors, which makes the operating frequency of the power conversion circuit Up to 50kHz. Apply new process components and adopt flexible switching technology to solve the high frequency limitation caused by switching loss and realize the high frequency of UPS power supply. The increase in the frequency of the conversion circuit greatly reduces the inductance, capacitance, noise, volume, etc. used for filtering, and greatly improves the UPS efficiency, dynamic response characteristics, and control accuracy.
(2) Redundant parallelization: In an electronic device, we can concentrate the control circuit as an independent pluggable module, or we can concentrate the power conversion part in a structure as a hot pluggable module Similarly, in a power supply system configured with multiple devices, we can also regard each device as a module. In the case of redundant hot backup configuration, failures can also be achieved. Then perform hot swap repair. The contemporary technologically advanced UPS has the direct parallel function. If two such UPSs are connected in redundant parallel, and the total output capacity of the two UPSs is greater than or equal to twice the load capacity, when one of them fails, the other One can bear the full load capacity and keep the system running normally, and the failed one can be repaired offline. This is tantamount to reducing the equivalent mean repair time of the system to close to zero. The system will stop running only when two UPSs fail at the same time, and this probability is very small.
(3) Digitization: Digital control has become the mainstream of the development of new UPS control technology. The digital controller has high precision, strong anti-interference ability, easy to realize the detection, fault diagnosis and isolation of UPS, easy to realize remote control and remote measurement, and realize multiple UPS The parallel connection and hot-swappable, easy to realize the monitoring and management of the battery. The power supply realized by digital control technology, data acquisition technology, signal processing technology, power management technology, network communication technology, computer hardware and software technology realizes the perfect combination of man and machine.
(4) Reliability: For users, UPS is required to have sufficient output capacity and reliability, otherwise it will affect the operation of the load and even constitute a new source of failure. Adopt advanced process packaging technology, highly integrated technology, use high-quality components and raw materials to continuously improve the reliability and availability of UPS power supplies, and strive for availability A of 0.9999999, that is, to allow downtime during the year Time≤3s. These data are the results that users really need.
(5) Intelligence: The application of microprocessors in UPS was only used in large and medium-sized UPS in the past, but in recent years it has gradually developed to small and micro UPS. The result is the intelligent development of UPS. Including control, detection and communication. UPS is gradually managed by computers, and computers and peripherals can "autonomously" cope with some possible foreseeable problems, and can perform automatic management and adjustments, such as automatically shutting down the host computer's operating system and turning off its power, and timing the UPS itself, etc. , And can transmit relevant signals to the operating system or network administrator through the network, which is convenient for remote management. Really achieve centralized computer monitoring instead of human duty, and computer intelligence realizes people's "dumb operation".
(6) Greening: Harmonic currents generated by various electrical equipment and power supply devices seriously pollute the power grid. With the introduction of various policies and regulations, the call for pollution-free green power supply devices is increasing. In addition to installing a high-efficiency input filter, the UPS should also adopt power factor correction technology at the input end of the power grid. This can eliminate the harmonic current generated by the rectifier filter circuit itself, and also compensate the input power factor. The rectifier uses IGBT technology, which can increase the input power factor to close to unity, and the pollution to the grid has been reduced to the level of a resistive load. In addition, high-frequency pulse width modulation technology, multi-pulse rectification technology, electromagnetic shielding and filtering technology, generalized soft switching technology, series-parallel compensation technology and other technologies are also effective ways to realize UPS greening.
(7) Economicalization: Low-cost and high-performance high-frequency machines will also become the mainstream models in the market after a period of time. This type of UPS eliminates the output isolation transformer on the basis of the above-mentioned future mainstream models, which greatly saves the cost, which is about 60% of the above-mentioned models, which is extremely competitive in the market. The disadvantage is that the current technology is not mature enough and the reliability is low. However, with the improvement of the technical level, the reliability will be greatly enhanced. It is believed that in the near future, this model will become the new mainstream model of UPS in the future.
3How to choose UPS
A UPS can be used for at least 3 years. When choosing a UPS power supply, users should determine the selection criteria according to their own requirements, and choose the UPS that best suits their business needs, rather than the cheapest or most high-end UPS.
(1) The user should have a comprehensive and clear understanding of the various indicators of UPS, which is a necessary condition for the correct and reasonable selection of UPS. UPS (indeed) is a constant voltage device that contains an energy storage device (battery) and a control circuit, with an inverter as the main component. Its main function is to provide a stable, clean, and high-quality power environment for the electrical equipment without interruption when the external power supply system is interrupted or exceeds the required range. (At present, according to its design principles and working methods, there are three types: line type, online type and online interactive type.) The user should fully understand the technical parameters, electrical performance and scope of application of various UPSs, and select them according to the characteristics of their own loads. UPS.
(2) While paying attention to the performance-price ratio, we must first pay attention to the output capacity and reliability of the UPS, the adaptability of the UPS to the grid, and the regular output performance indicators of the UPS. Pay special attention to whether the purchased UPS can reach the UPS that has been issued by the country. Manufacturing specifications.
(3) Because the purchase of batteries occupies a large part of the UPS purchase cost, and the operating conditions and service life of the batteries directly affect the performance of the UPS functions, it is necessary to purchase a UPS with intelligent battery management technology.
(4) It is necessary to purchase UPS with power factor correction technology, current harmonic suppression technology, electromagnetic compatibility design technology, and silent design technology.
(5) Try to use famous-brand UPS products from well-known companies. Because these companies not only have complete testing equipment, advanced capabilities, and the ability to guarantee product quality, but also have a strong sense of service, can actively provide users with pre-sales, in-sales, and after-sales services, and respond quickly to user information. .
In order to ensure the safe and reliable operation of the UPS system, when selecting a UPS, its anti-lightning and anti-surge capacity, overload capacity, load capacity, maintainability, manageability and other factors should also be considered. In short, UPS is indeed the core equipment of the power supply system. How to choose and configure UPS is very important to users. You should try your best to choose and configure cost-effective UPS to ensure safe and reliable uninterrupted power supply for your equipment.